The option TracUriRoot may or may not be necessary in your setup. Try your configuration with out it, and if the URLs produced by Trac look wrong or if Trac does not seem to recognize the URLs correctly, add the TracUriRoot option. You will notice that the Location and TracUriRoot have the same path.

When you request the /projects URL, you will get a listing of all subdirectories of the directory you set as TracEnvParentDir that look like Trac environment directories. Selecting any project in the list will bring you to the corresponding Trac environment.

If you don't want to have the subdirectory listing as your projects home page you can use a

<LocationMatch "/.+/">

This will instruct Apache to use mod_python for all locations different from root while having the possibility of placing a custom home page for root in your DocumentRoot folder.

You can also use the same authentication realm for all of the projects using a <LocationMatch> directive:

Troubleshooting

In general, if you get server error pages, you can either check the Apache error log, or enable the PythonDebug option:

<Location /projects/myproject>
...
PythonDebug on
</Location>

Form submission problems

If you're experiencing problems submitting some of the forms in Trac (a common problem is that you get redirected to the start page after submission), check whether your DocumentRoot contains a folder or file with the same path that you mapped the mod_python handler to. For some reason, mod_python gets confused when it is mapped to a location that also matches a static resource.

Problem with virtual host configuration

If the <Location /> directive is used, setting the DocumentRoot may result in a 403 (Forbidden) error. Either remove the DocumentRoot directive, or make sure that accessing the directory it points is allowed (in a corresponding <Directory> block).

Using <Location /> together with SetHandler resulted in having everything handled by mod_python, which leads to not being able download any CSS or images/icons. I used <Location /trac> SetHandler None </Location> to circumvent the problem, though I do not know if this is the most elegant solution.

Using .htaccess

Although it may seem trivial to rewrite the above configuration as a directory in your document root with a .htaccess file, this does not work. Apache will append a "/" to any Trac URLs, which interferes with its correct operation.

It may be possible to work around this with mod_rewrite, but I failed to get this working. In all, it is more hassle than it is worth. Stick to the provided instructions. :)

Win32 Issues

If you run trac with mod_python < 3.2 on Windows, uploading attachments will not work. This problem is resolved in mod_python 3.1.4 or later, so please upgrade mod_python to fix this.

OS X issues

When using mod_python on OS X you will not be able to restart Apache using apachectl restart. This is apparently fixed in mod_python 3.2, but there's also a patch available for earlier versions here.

SELinux issues

If Trac reports something like: Cannot get shared lock on db.lock
The security context on the repository may need to be set:

chcon -R -h -t httpd_sys_content_t PATH_TO_REPOSITORY

See also [http://subversion.tigris.org/faq.html#reposperms]

FreeBSD issues

Pay attention to the version of the installed mod_python and sqlite packages. Ports have both the new and old ones, but earlier versions of pysqlite and mod_python won't integrate as the former requires threaded support in python, and the latter requires a threadless install.

Subversion issues

If you get the following Trac Error Unsupported version control system "svn" only under mod_python, though it works well on the command-line and even with TracStandalone, chances are that you forgot to add the path to the Python bindings with the PythonPath directive. (The better way is to add a link to the bindings in the Python site-packages directory, or create a .pth file in that directory.)

If this is not the case, it's possible that you're using Subversion libraries that are binary incompatible with the apache ones (an incompatibility of the apr libraries is usually the cause). In that case, you also won't be able to use the svn modules for Apache (mod_dav_svn).